This invention relates to liquid depth measuring apparatus and methods, such as for example, are used in flow-rate measurements and in liquid sampling.
One class of flow meter performs depth measurements in a known flow path. For such a measurement, a depth measuring instrument such as a bubbler is used. The known flow paths may be controlled by a movable gate or obstruction in a flow stream that alters the flow to enable easier measurement of flow rate.
In one type of prior art bubbler, clogging is reduced by purging the outlet orifice of the bubbler from time to time with a faster flowing stream of air to clear the orifice. One such bubbler includes a purge system that accumulates air under pressure in a tank and opens the tank periodically to cause a high pressure surge of air to clear the bubbler.
In a prior art purge system of this type, the purge system includes a solenoid operated valve to open the tank to the bubbler line. The tanks have been generally located near a controller and remote from the bubbler outlet port. It has from time to time been proposed to locate the tank closer to the outlet port of the bubbler but this it not known to have been implemented. The prior art arrangement in which a solenoid operated valve opens an air tank near the controller has the disadvantage of requiring a long air line between the solenoid operated valve and the bubbler outlet and the proposed system with a tank close to the bubbler outlet would have had the disadvantage of requiring an electric line to a location in or near the water. Long electric lines increase the possibility of explosions from methane gas.